I bought a book from Amazon the other day and when it arrived it had a massive crease all down the front cover. I wrote to them straight away about it and they offered me a full refund and let me keep the book which was okay.
I think you were completely in the right to complain. When you buy stuff from Amazon you really don't expect it to be creased up or bent and they have to be aware that the people packing the goods aren't doing it right.